From 4dbc5d9f4f791df8a5879f4a655f517adc7f56d1 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Fri, 20 Jan 2012 16:16:59 +0800 Subject: virtio: fix typos of memory barriers Note: this fixes a bug introduced recently in 7b21e34fd1c272e3a8c3846168f2f6287a4cd72b. Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: Rusty Russell --- drivers/virtio/virtio_ring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/virtio') diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 79e1b292c030..78428a863b46 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -35,7 +35,7 @@ #define virtio_rmb(vq) \ do { if ((vq)->weak_barriers) smp_rmb(); else rmb(); } while(0) #define virtio_wmb(vq) \ - do { if ((vq)->weak_barriers) smp_rmb(); else rmb(); } while(0) + do { if ((vq)->weak_barriers) smp_wmb(); else wmb(); } while(0) #else /* We must force memory ordering even if guest is UP since host could be * running on another CPU, but SMP barriers are defined to barrier() in that -- cgit v1.2.3 From a72caae21803b74e04e2afda5e035f149d4ea118 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Fri, 20 Jan 2012 16:17:08 +0800 Subject: virtio: correct the memory barrier in virtqueue_kick_prepare() Use virtio_mb() to make sure the available index to be exposed before checking the the avail event. Otherwise we may get stale value of avail event in guest and never kick the host after. Note: this fixes a bug introduced by ee7cd8981e15bcb365fc762afe3fc47b8242f630. Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: Rusty Russell Cc: stable@kernel.org --- drivers/virtio/virtio_ring.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/virtio') diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 78428a863b46..5aa43c3392a2 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -308,9 +308,9 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq) bool needs_kick; START_USE(vq); - /* Descriptors and available array need to be set before we expose the - * new available array entries. */ - virtio_wmb(vq); + /* We need to expose available array entries before checking avail + * event. */ + virtio_mb(vq); old = vq->vring.avail->idx - vq->num_added; new = vq->vring.avail->idx; -- cgit v1.2.3